NK-33

The NK-33 (GRAU index: 14D15) and its vacuum-optimized variant, the NK-43, were rocket engines developed in the late 1960s and early 1970s by the Kuznetsov Design Bureau for the Soviet space program's ill-fated N1 Moon rocket. The NK-33 is among the most powerful LOX/RP-1 powered rocket engines ever built, noted for its high specific impulse and low structural mass. The NK-33 was an improved version of the earlier NK-15 engine, which powered the original N1 launch vehicle. Key upgrades included simplified pneumatic and hydraulic systems, advanced controls, enhanced turbopumps, an improved combustion chamber, fewer interfaces employing pyrotechnic devices, and modified interfaces to facilitate replacement of parts during refurbishment. Each N1F rocket would have utilized 30 NK-33 engines on its first stage and eight NK-43 engines on its second stage. Consequently, when the Soviet Union aborted its lunar landing effort in 1974, dozens of already manufactured engines were left in storage. Decades later, they found new life powering the first stage of the American Antares 100 and the Russian Soyuz-2.1v rockets. The supply of NK-33 engines was reportedly exhausted by early 2025. Russia planned to replace the NK-33 on the Soyuz-2.1v with the RD-193 engine.